Process for production of potassium carbonate



June 1l, 1929.` R. D. PIKE T Ax. 1,716,663

PROCESS FOR PRODUCTION OF POTAS'SIUM CARBONATE 'Filed March 6,'1928 ATTORNEYS.

Patented June 11, 1929.

UNITED STATES PATENT oFFlcE.`

. ROBERT D. PIKE, OFPIEDMON T, 4LEO V. STECK, OF OAKLAND, AND ROSS CUiMMINGS, 0E BERKELEY, CALIFORNIA; SAID STECK AND SAID CUMMINGS ASSIGNORS T0 SAID'- PIKE.

PROCESS FOR PRDUCTION OF PO'IASSIUM CARBONA'IE. l

Application filed March 6, 1928. Serial No. 259,423.

Our present invention relates to a method for producing commercially pure potassium carbonate from brine carrying the carbonatos of sodium and potassium and more particularly to such a method for treatment-of the crude potassium-carbonate brine which is the principal product of a process covered by a copcnding application filed concurrently herewith by us and identified as case (QJ.

The above crude potassium carbonate has aV mol ratio KZC/Naz() vof 3.26 and by our present invention this same mol ratio may be increased to 12/ 1, or higher, to the end that commercially pure potassium carbonate in solid form lnay be produced directly from the purified brine.

In general our invention is based upon the use of base exchange zeolites of the Water softening type for effecting separation of sodium from potassium in the crude brine. In lour process the crude brine is run over a potash zeolite for` removal of sodium from the brine and its replacement with potassium, and after the. potash zeolite has become exhausted regenerating it by passing over it a solution of substantially pure muriate of potash.

A preferred method of carrying out our process is shown in the accompanyingl drawing.

The zeolite is. stored in suitable tanks 1 and 1b which are` used alternately for run and ifregeneration, and is supported therein upon a porous false bottom. We Will assume 4 that the tank 1b is readyfor`the run, which means that the zeolite which it contains is potash zeolite, and that the regenerating' solution has been drained off, and that the potash zeolite has been Washed free from chloride.

The crude potassium carbonate brine containy ing 5% to 10% total soli ds is stored in a tank 2 and is pumped through a pipe line 3.

During this operation the valve 3b is open and valve 3L is shut. The brine is then pumped up through the zeolite in tank 1b at a very rapid rate corresponding to about ten gallons per square foot of horizontal area per minute. visible at the top of the tank 1", the rate is cut down to one-half gallon per minute per square foot. The purpose of the high initial jrate of How is to `displace air from the intery stices between the zeolite particles, but this rate of .'floW is too highfor efficientbase exchange. The brine issues from the top of the As .soon as the flow becomes tank as a purified brine of potassium carbonate and flows out through a pipe 4:. The valve 4 is open and the valve 4 is shut during this operation. At first the brine is a practically pure solution of potassium carbonate, but as the flow proceeds the sodium carbonate increases and the time of flow is regulated by thc requirements for purity in the total flow of the purified brine.

Ina typical case, starting with a crude brine containing'5% total solids, the reaction time is fifty-two minutes to give an eiiluent whose solid content contains on' the average 96.2% by weight K2CO3. At the end of the run the valves 3b and etbare closed and valves 5l and 5 are opened to allow the liquid convtents of tank 1b to drain back into tank 2.

Valve 61 is now opened and the zeolite in 1 is washed to remove carbonates and the ings also drain into tank 2. Tank 1b .is nijiv1 of pumping are the same as those observed y with the crude potassium ,carbonate brine.

The potassium in the KCl brinereplaces the sodium in the zeolite veryrapidly; the latter passes into solution, and in about ten to iiftecli minutes the zeolite is restored to the potash rich condition and is ready'for another run. The effluent durlng regeneratlon passes through a valve 9" and via pipe 9 into a f tank 10. After regeneration, valve 6b isagain open and the chlorides Washed out of the zeolites, the Washingsof this operation draining through valves 5b and 11 into the tank 10. After washing and draining, these valves are reset-as at the beginning of the above described cycle and the tank 1h is ready for another run. The cycle of tank 1a is the same as 1b, and for continuous are used alternately. f

In practice more than two tanks can be used if desired so as to insure a. substantially uniform flow. The tank 10 contains a solution of potassium chloride, with some sodium.'

lgeneration. It is also necessary. to add KCl to make up for that actually converted to 'NaCl in the process of regeneration. The solution. from tank 10 is therefore run through lmultiple eifectevaporators 12 in'which KCl operation they ion liii the crude carbonate 13 of any suitable design. T he motherliquor and washnrwater from these crystals. is re turned into the evaporator circuit. vEvaporation is continued until the solution is nearly saturated with NaCl. The strong liquor goes to' crystallizer 14; where KCl is crystallized out by cooling and is removed in centrifuge 15 the mother liquor from these crystals contains much NaCl and some KCI and is preferably removed from the process to a tank 16 for treatment elsewhere.` The water used for washing the crystals in the centrifuge 15 goes back to the evaporator circuit via the tank 10. The KCl crystals goto tank 7 where they are dissolved in water preparatory to being again employed for regenerating the zeolite. The make up KCl is added to tank 7.

In effect, substantially all of the sodium brine is replaced-bj)7 its equivalent potassium, the latter being brought in as potassium vchloride and the chlorine associated with the latter is rejected from the system as sodium chloride in association with the sodium of the crude carbonate brine. It is thus seen that no reagents are actually used up, and the principal cost of the process is for fuel for evaporating.

We have found that zeolites which are commercially available as water soft-eners are suitable for our process, and it is necessary to keep in the tanks from three to iive tons of zeolite for each ton of K2O produced daily as the carbonate.

While We have described a preferred method of'carrying out our invention,`it lis to be understood that various changesy may be made between the limits herein set forth and in the sequence of operations without departing from the spirit of the invention as defined in the appended claims Having thus described our invention, what we claim and desire to secure by Letters Patent is 1. The process for separating the potassium and sodium contents of carbonate brine vwhich consists in passing the brine overy a potash zeolite thus replacing sodium in the brine with potassium from the zeolite, and

regenerating the Zeolite with a solution of awhich consists in passing the brine over a potash zeolite, thus replacing sodium in the brine with potassium 'from the zeolite, tlicn regenerating the Zeolite with a solution of potassium chloride, and treating the spent regenerating solution by evaporation and crysvtallization for removal of sodium chloride and recovery of potassium chloride. n

4 The process of removing sodium from a. mixed brine of potassium and sodium carbonate which consists in passing the brine over a potash zeolitc which will give up potassium to and remove sodium from the brine.

` ROBERT D. PIKE.

LE() V. STECK. ROSS CUMMINGS. 

